The Maxwell Creek Watershed Project (MCWP or “the Project”) is tackling the complexities of addressing cumulative impacts of climate change on local ecosystems while also navigating interagency collaboration. The ultimate goal of the Project is to better understand and define the efficacy of nature-based solutions, such as the installation of green infrastructure, in increasing climate resilience and enhancing ecological integrity and biodiversity.
There are three actionable objectives of the Project:
The Maxwell Creek Watershed was chosen as an area of focus for a number of reasons. Not least of which is that it is essential to the resilience of the Salt Spring Island community. It supplies potable water to nearly 50% of year-round island residents, including the Village of Ganges and the hospital. Maps 1 through 21 will provide additional information about the study area, land-use history, and many other additional details that have been considered in the design, and included in the and implementation of the MCWP.
Mount Maxwell, also known as Hwmet’utsum to the Hul’q’umi’num speaking peoples, is an important ecological feature of Salt Spring Island, BC. The mountain is the highest peak in the Gulf islands standing at 602 metres tall and comprises various unique ecosystems including second growth Coastal Douglas-fir forests, garry oak woodlands, and wetland habitat. Hwmet’utsum has gained ecological interest due to the unique history of logging, agriculture, and wildfire on the landscape. Specifically, the Maxwell Creek Watershed, extending over 296 acres of protected land, is the main area of interest. The Maxwell Creek Watershed project was initiated to understand and enhance the ecological integrity of the forests and wetland areas in this watershed through restoration and wildfire resilience.
Map 1: Capital Regional District watersheds on Salt Spring Island. Maxwell Creek Watershed is outlined in red.
Map 2: Salt Spring Island. Maxwell Creek Watershed is outlined in red and Maxwell Lake is highlighted in blue. The watershed is currently well protected through private and public covenants, protected areas, and parks.
The Maxwell Creek Watershed highlighted in red, with green circle indicating the study area of the Maxwell Creek Watershed Project. Water runs through the watershed from the southeast corner (near Maxwell Provincial Park) to the north-north west. Much of the upper watershed, which supports the water supply to Maxwell Lake, is owned and under the management of the local Improvement District, North Salt Spring Waterworks District, which has been delivering water to the community since 1914.
To provide some examples of the mapping work being done for the Maxwell Creek Watershed Project, thumbnail maps from the area circled have been provided in Maps 5 through 17. The focus of the MCWP is in the area immediately around Maxwell Lake, a large part of which is owned and stewarded by NSSWD.
Aerial imagery provides a historic record of land-use change over time. These images are essential to understanding baseline ecological conditions. As shown in the image above, timber harvest was once a large-scale and recurring activity within the Maxwell Creek Watershed. This explains the structural and age homogeneity within present-day forests in this area. Compare this photo (taken in 1957) with the satellite and bare earth images in Maps 6 & 7. The site of the original Maxwell Farmstead appears in the top left.
Considerations: Aerial photos may be obtained at a cost (Digital Air Photos of B.C. - Province of British Columbia. Images are not georeferenced, and technical skills are required to process and interpret images.
Similar to aerial imagery, but taken at a much wider geographic scale and at a higher level of detail, satellite imagery provides snapshots in time of the different features (e.g. buildings, roads, vegetation) on the Earth’s surface. In the ecological context, scientists and other practitioners can identify and differentiate features at a landscape level, helping to identify potential sites for collecting information on vegetation coverage, canopy, and changes in land cover over time.
Natural regeneration since 1946, and abandonment has closed much of the canopy in this area. Intrusion into the old farmstead by trees is visible, and a site visit showed that the remaining open area is due to a high water table in the area. The site was formerly a wet meadow.
This LiDAR Digital Elevation Model (DEM) covers the same area seen in Maps 5 and 6. However, rather than treetops it shows the bare earth surface and reveals, along with the geological features, human disturbance - such as old roadbeds, many of which are now trails or access routes, ditches, and agricultural drainage - and other items of interest not visible with aerial photography. In other words, it shows what is under the trees.
This map shows several depressions where water is able to accumulate, including the former farm site (top left).
Considerations: Bare earth information is incredibly useful for highlighting linear features and exposing hidden features. For example, linear features in the former farm fields run perpendicular to the movement of water, serving as drainage and irrigation infrastructure. Although the farm has not operated in over 20 years, the drainage system remains, meaning without its removal the wet meadow will be unable to recover.
Light Detection and Ranging (LiDAR) provides detailed and accurate three-dimensional characterization of vertical forest structure, including tree height, basal area, and even tree type.
As the MCWP is focused on fire, and preventing the movement of fire into the canopy (i.e., reducing potential catastrophic canopy fire), the high density of trees and absence of natural gaps and structural complexity using LiDAR informs fire hazard and risk assessment.
Considerations: LiDAR interpretation requires advanced GIS technical abilities.
LiDAR tree height information helps to highlight specific information that may not otherwise be apparent.
In this case, the tallest trees are shown in green, and the shortest canopy (trails/low shrubs/grasses) are shown in yellow and pale brown. This information has proven extremely valuable in detecting areas of higher soil moisture, even when there are no streams or wetlands present (due to extent of ditching, draining, etc).
The green area of tall trees indicates areas of good growing conditions, and provides information about potential water availability across the landscape.
Satellite data can be used over time to map out areas of harvest. Organizations like Global Forest Watch produce annual maps showing the area of forest lost (since 2020). This type of information allows tree age and regeneration to be evaluated from a ‘zero’ or baseline year.
Official planting and harvesting maps are sometimes available. In this case detailed breakdowns of cut blocks and their delineations are provided. If the limits of blocks in this map (from December, 2000) are compared to the variation in tree canopy in Map 10, the influence of these cutblocks is still visible on the landscape.
Considerations: These maps can be hard to track down and are often not available in digital format. They provide additional information about trees harvested and historic forest attributes. However, expertise is required to interpret this information.
The British Columbia VRI is used to describe the location of a resource (e.g. trees to be harvested) and the amount of timber/woody material in a given unit area. VRI begins with photo interpretation to estimate vegetation features within polygons, and is followed by ground sampling to collect the detailed information about tree age, basal area, tree height, volume and composition, as well as ecological characteristics.
Considerations: Although a generalized representation of forest characteristics, and forestry-derived, VRI units provide useful information about forest stands and are comparable to Terrestrial Ecosystem Mapping (TEM) or Sensitive Ecosystem Inventory (SEI) polygons.
The Maxwell Creek watershed resides within the Coastal Douglas-fir (CDF) forest biogeoclimatic zone, which when mature provides resilience to fires due to its multi-layered canopy, abundance of coarse woody debris, and deep root networks. Fire disturbance regimes are natural in this forest type, occurring periodically as stand-replacing events that take place on >100 year return cycles. Fire data indicates wildfire occurrences in the watershed throughout the 1930’s and 1940’s, and as recently as 2009. While in the surrounding areas, wildfires were recorded through the years of 1952, 1956, 1959, 1982, 1987, 1989, 1995, and 2008. Data on the severity of these fires are limited, however, visual fire damage is evident at the site. Historical logging of the Maxwell Creek watershed throughout the second half of the 20th century may play a role in the occurrence of such fires, due to diminished forest structure and complexity.
Base rock layers - or local geological layers - can provide information about soils and the movement of water. Salt Spring and other Gulf Islands are characterised by glaciated ridges and valleys that reflect the geometries of the underlying bedrock formations. The islands are underlain by highly faulted sedimentary rocks of the Nanaimo Group. Groundwater aquifers in the bedrock are important ecologically and as a community water supply, but are poorly understood and difficult to map because they are highly partitioned (often in faults).
Considerations: This map’s resolution is low.
The Maxwell Creek watershed is characterised by ridges of erosion-resistant sandstone and conglomerate and lower valleys with eroded materials, such as shales, gravelly sand loam, and colluvial materials and a C-horizon consists of fractured bedrock. The Maxwell farmstead was placed on Suffolk soil, which is characterised as loamy sand.
The CDF Biogeoclimatic Zone ranges in elevation with ecosystems varying according to aspect, soils, and other biophysical conditions. The topography and ecological niches across the Maxwell Creek Watershed are diverse; ranging from just under 300 m elevation, including valleys, wetlands, rocky ridges and ravines. Maxwell Creek ends at the Stuart Channel just north of Erskin Point (an area of suitable Surf smelt forage and spawning habitat).
Contour lines show elevation over sea level. Lines that are close together indicate steep slopes, lines that are farther apart indicate gentle slopes. Contour maps are important in the context of the MCWP, influencing surface water flows, water accumulation, and vegetation and tree cover.
Considerations: Contour data is readily accessible and useful for identifying features in the landscape. It is also useful in models seeking to map surface water flows or identify catchment areas.
Bare Earth information is used in surface-water modelling to understand how water flows within the watershed. In this map, drainage channels (shown) were derived from surface topography to show overland flow.
The Maxwell farmstead (top left) shows how water has been rerouted using linear features within the fields, and using a trench running east-west immediately south of the farm. These features accelerate water flows and exacerbate flash flooding and erosion. In fact, the trench intercepts and redirects the waters from the upper watershed away from the fields, toward the Maxwell Road - which is experiencing significant erosion and contributing to sediment and nutrient loading into the creek supplying Maxwell lake.
Maxwell Creek Watershed is outlined in red and Maxwell Lake is highlighted in blue. Property lines and detail shown in white. Cadastral data layers are essential to this project as they denote land ownership and thus what land-use activities are/are not permitted.
Maxwell Creek Watershed is outlined in red and Maxwell Lake is highlighted in blue. Parks (light green), EcoReserves (yellow), Watershed protection (hatched), covenants (pink). are shown.
This information is important to help us delineate the areas we include in the study, and to connect with landowners to let them know about the project.
These are areas designated as requiring permissions and limiting the types of activities that may be undertaken. Lake Maxwell is within a DPA for Lakes, Streams and Wetlands (Island Trust).
Drainage patterns and watershed sub-basins calculated from a Lidar digital elevation model DEM. The Maxwell Creek Watershed is shown with a red line. Watershed sub-basin A feeds directly into the lake, the upper part of sub-basin B can be diverted into the lake at D, water from sub-basin C does not flow into the lake. Surveyed RAR watercourses shown in blue. Watershed sub-basins are derived from a LIDAR digital elevation model.